/*
 * Until FreeBSD gets their act together;
 * http://www.mail-archive.com/freebsd-hackers@freebsd.org/msg69469.html
 */
#if defined(FREEBSD)
#undef _XOPEN_SOURCE
#endif

#if defined(FREEBSD) || defined(DRAGONFLYBSD)
#include <sys/types.h>
#else /* OPENBSD || NETBSD */
#include <sys/param.h>
#endif
#include <sys/sysctl.h>

#include <assert.h>

#if defined(OPENBSD)
#include <kvm.h>
#include <limits.h> /* _POSIX2_LINE_MAX */
#endif

#include <stdio.h>
#include <stdlib.h>

#if defined(OPENBSD)
#include <string.h>
#endif

#include <unistd.h>

#include "WMdefs.h"
#include "osdep.h"

/*
 * copy argc and argv for an existing process identified by `pid'
 * into suitable storage given in ***argv and *argc.
 *
 * subsequent calls use the same static area for argv and argc.
 *
 * returns 0 for failure, in which case argc := 0 and argv := NULL
 * returns 1 for success
 */
/*
 * NetBSD, FreeBSD and DragonFlyBSD supply the necessary information via
 * sysctl(3). The result is a plain simple flat octet stream and its length.
 * The octet stream represents argv, with members separated by a null character.
 * The argv array returned by GetCommandForPid() consists of pointers into this
 * stream (which is stored in a static array, `args'). Net and Free/DFly only
 * differ slightly in the MIB vector given to sysctl(3). Free and DFly are
 * identical.
 *
 * OpenBSD supplies the necessary informationvia kvm(3) in the form of a real
 * argv array. This array is flattened to be in the same way as Net/Free/DFly
 * returns the arguments in the first place. This is done in order for the
 * storage (`args') to easily be made static, which means some memory bytes
 * are sacrificed to save hoops of memory management.
 */
Bool GetCommandForPid(int pid, char ***argv, int *argc)
{
  /*
   * it just returns failure if the sysctl calls fail; since there's
   * apparently no harm done to the caller because of this, it seems
   * more user-friendly than to bomb out.
   */
  int j, mib[4];
  unsigned int i;
  size_t count;
  static char *args = NULL;
  static int argmax = 0;
#if defined(OPENBSD)
  char kvmerr[_POSIX2_LINE_MAX]; /* for kvm*() error reporting */
  int procs;                     /* kvm_getprocs() */
  kvm_t *kd;
  struct kinfo_proc *kp;
  char **nargv; /* kvm_getarg() */
#endif

  *argv = NULL;
  *argc = 0;

  /* the system-wide limit */
  if (argmax == 0) { /* it hopefully doesn't change at runtime *g* */
    mib[0] = CTL_KERN;
    mib[1] = KERN_ARGMAX;
    mib[2] = 0;
    mib[3] = 0;

    count = sizeof(argmax);
    if (sysctl(mib, 2, &argmax, &count, NULL, 0) == -1)
      return False;
  }

  /* if argmax is still 0, something went very seriously wrong */
  assert(argmax > 0);

  /* space for args; no need to free before returning even on errors */
  if (args == NULL)
    args = (char *)wmalloc(argmax);

#if defined(OPENBSD)
  /* kvm descriptor */
  kd = kvm_openfiles(NULL, NULL, NULL, KVM_NO_FILES, kvmerr);
  if (kd == NULL)
    return False;

  procs = 0;
  /* the process we are interested in */
  kp = kvm_getprocs(kd, KERN_PROC_PID, pid, sizeof(*kp), &procs);
  if (kp == NULL || procs == 0)
    /* if kvm_getprocs() bombs out or does not find the process */
    return False;

  /* get its argv */
  nargv = kvm_getargv(kd, kp, 0);
  if (nargv == NULL)
    return False;

  /* flatten nargv into args */
  count = 0;
  memset(args, 0, argmax);
  /*
   * must have this much free space in `args' in order for the current
   * iteration not to overflow it: we are at `count', and will append
   * the next (*argc) arg and a nul (+1)
   * technically, overflow (or truncation, which isn't handled) can not
   * happen (should not, at least).
   */
#define ARGSPACE (count + strlen(nargv[(*argc)]) + 1)
  while (nargv[*argc] && ARGSPACE < argmax) {
    memcpy(args + count, nargv[*argc], strlen(nargv[*argc]));
    count += strlen(nargv[*argc]) + 1;
    (*argc)++;
  }
#undef ARGSPACE
  /* by now *argc is correct as a byproduct */

  kvm_close(kd);
#else /* FREEBSD || NETBSD || DRAGONFLYBSD */

  mib[0] = CTL_KERN;
#if defined(NETBSD)
  mib[1] = KERN_PROC_ARGS;
  mib[2] = pid;
  mib[3] = KERN_PROC_ARGV;
#elif defined(FREEBSD) || defined(DRAGONFLYBSD)
  mib[1] = KERN_PROC;
  mib[2] = KERN_PROC_ARGS;
  mib[3] = pid;
#endif

  count = argmax;
  /* canary */
  *args = 0;
  if (sysctl(mib, 4, args, &count, NULL, 0) == -1 || *args == 0)
    return False;

  /* args is a flattened series of null-terminated strings */
  for (i = 0; i < count; i++)
    if (args[i] == '\0')
      (*argc)++;
#endif

  *argv = (char **)malloc(sizeof(char *) * (*argc + 1 /* term. null ptr */));
  (*argv)[0] = args;

  /* go through args, set argv[$next] to the beginning of each string */
  for (i = 0, j = 1; i < count; i++) {
    if (args[i] != '\0')
      continue;
    if (i < count - 1)
      (*argv)[j++] = &args[i + 1];
    if (j == *argc)
      break;
  }

  /* the list of arguments must be terminated by a null pointer */
  (*argv)[j] = NULL;
  return True;
}
